Muhammad bin al-Munkadir (may Allah have mercy on him) narrates: I heard Sayyiduna Jabir (may Allah be pleased with him) say: The Jews used to say that whoever approaches his wife from behind but in her private part, the child born will be cross-eyed. So Allah the Exalted revealed this verse: "Your wives are a place of sowing for you, so come to your place of sowing however you wish" (__QUR_N__). That is, you may approach your wife in any manner, but intercourse should only be through the lawful (natural) way.